The present invention relates to devices for forming a thread chain on a multiple-needle chainstitch sewing machine.
In two-needle overedge sewing machines, German Patent Specification No. 37 05 263 discloses an overedge stitch of stitch type 506 of Class 500 in accordance with INTERNATIONAL STANDARD ISO 1/3 4915-1981 (E/F) or German Standard DIN 61400, Duetsches Institut fuer Normung e.V. (German Standardisation Institute), May 1988 Edition, following the formation of a sewing seam on a workpiece with the aid of a chainstitch forming tongue disposed on the side adjacent to a needle hole, to form not only a sewing seam on the workpiece, but also a thread chain without a workpiece. This thread chain, which is formed by a plurality of sewing stitches, makes it possible for a problem-free commencement of the seam to be formed on the edge of a further workpiece to be sewn.
With conventional needle plates in multiple-needle chainstitch sewing machines for a Class 400 double chain stitch, e.g., stitch type 406 or 407, and/or for a double chain stitch having a Class 600 cover thread, for example stitch type 602, 605, in accordance with the above-mentioned standards, it is not possible to form, with sufficient reliability, a thread chain having a plurality of stitches without a workpiece, since, because of the missing workpiece, the sewing threads are positioned irregularly and incorrectly in the stitch formation region.